Lithium-free ion exchangeable glasses

Abstract

A glass composition includes: from 50 mol % to 70 mol % SiO 2 ; from 15 mol % to 30 mol % Al 2 O 3 ; from 5 mol % to 20 mol % Na 2 O; from 0 mol % to 15 mol % MgO; and from 0 mol % to 15 mol % CaO. The glass composition is free or substantially free of Li (i.e., Li 2 O). The sum of MgO and CaO in the glass composition may be from 0 mol % to 30 mol %.

1 . A glass composition comprising:
 greater than or equal to 50 mol % and less than or equal to 70 mol % SiO 2 ;   greater than or equal to 15 mol % and less than or equal to 30 mol % Al 2 O 3 ;   greater than or equal to 5 mol % and less than or equal to 20 mol % Na 2 O;   greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and   greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and
 RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO. 
   
     
     
         2 . The glass composition of  claim 1 , wherein the glass composition comprises greater than or equal to 16 mol % and less than or equal to 28 mol % Al 2 O 3 . 
     
     
         3 . The glass composition of  claim 1 , wherein the glass composition comprises greater than or equal to 7 mol % and less than or equal to 18 mol % Na 2 O. 
     
     
         4 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 13 mol % MgO. 
     
     
         5 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 13 mol % CaO. 
     
     
         6 . The glass composition of  claim 1 , wherein RO is greater than or equal to 1 mol % and less than or equal to 25 mol %. 
     
     
         7 . The glass composition of  claim 1 , wherein (Na 2 O+RO)/Al 2 O 3  is greater than or equal to 0.5 and less than or equal to 1.5. 
     
     
         8 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 5 mol % P 2 O 5 . 
     
     
         9 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 10 mol % Y 2 O 3 . 
     
     
         10 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 5 mol % ZrO 2 . 
     
     
         11 . The glass composition of  claim 1 , wherein the glass composition comprises greater than 0 mol % and less than or equal to 1 mol % SnO 2 . 
     
     
         12 . The glass composition of  claim 1 , wherein the glass composition has a Young's Modulus greater than or equal to 60 GPa. 
     
     
         13 . The glass composition of  claim 1 , wherein the glass composition has a fracture toughness greater than or equal to 0.75 MPa·m 1/2 . 
     
     
         14 . The glass composition of  claim 1 , wherein the strain point is greater than or equal to 600° C. 
     
     
         15 . A method of forming a glass article, the method comprising:
 heating a glass composition, the glass composition comprising:
 greater than or equal to 50 mol % and less than or equal to 70 mol % SiO 2 ; 
 greater than or equal to 15 mol % and less than or equal to 30 mol % Al 2 O 3 ; 
 greater than or equal to 5 mol % and less than or equal to 20 mol % Na 2 O; 
 greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and 
 greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and
 RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO; and 
 
   cooling the glass composition to form the glass article.   
     
     
         16 . The method of  claim 15 , further comprising strengthening the glass article in a first ion exchange bath at a temperature greater than or equal 500° C. for a time period greater than or equal to 1 hour and less than or equal to 32 hours to form an ion exchanged glass article. 
     
     
         17 . The method of  claim 16 , further comprising strengthening the glass article in a second ion exchange bath at a temperature greater than or equal to 300° C. for a time period greater than or equal to 1 hour and less than or equal to 32 hours to form an ion exchanged glass article. 
     
     
         18 . The method of  claim 16 , wherein the ion exchanged glass article comprises a surface compressive stress greater than or equal to 350 Mpa and less than or equal to 900 MPa, and a depth of compression greater than or equal to 80 μm. 
     
     
         19 . The method of  claim 15 , wherein the first ion exchange bath, the second ion exchange bath, or both comprises KNO 3 . 
     
     
         20 . The method of  claim 15 , wherein the first ion exchange bath, the second ion exchange bath, or both comprises NaNO 3 .